1. Field of the Invention
The present invention relates to a radiology stand, particularly intended for radio diagnosis and which permits isocentric exploration or examination of a patient with a multitude of angles.
2. Description of the Prior Arts
Radiological examination of a patient is accomplished by means of an image chain which generally consists essentially of an X-ray source, a collimator, an anti-diffusion grid and an image receiver, supported by the stand and rigidly interconnected together, said X-ray source and collimator being on the same side of the patient to be examined while the anti-diffusion grid and the same image receiver are on the other side. A straight line passing through the center of the X-ray source and the center of the image receiver represents the X-ray axis or the image chain axis which during examination or isocentric exploration, always passes through the area to be analyzed at the same point whatever the orientation of this axis which constitutes the isocenter; the movement by which the orientation of the image chain can be varied while maintaining a fixed position with respect to the isocenter which referred to as the isocentric movement.
The stands which make this isocentric movement possible generally include an open arc curved support, one end of which supports an X-ray source while the other bears an image receiver. The image chain axis formed between the image receiver and the X-ray source passes through the isocenter, said isocenter forming the center of the arc or being on the same axis as the center of the arc in such a way that an isocentric movement is obtained by turning the arc about itself within its own plane around its center, while the arc is made to slide within a sleeve in the form of a semi-circular arc, for instance.
A similar arrangement is used both for large and extensive X-ray systems in which the arc movements are motor-driven as in the case of small X-ray systems such as mobile surgical units or mammaliographs for instance in which the image chain is not excessively heavy so that the arc movements need not be motordriven; these movements can be obtained by simple manual action by the operator.
In addition, it will be observed that these different radiology stands also permit another isocentric movement which consists of the rotation of the arc plane about a second axis rotation perpendicular to the first, also passing through the isocenter.
One of the drawbacks inherent in such an arrangement is that when the axis of the image chain is parallel to this second axis, there is no modification in its angle of incidence due to the second isocentric movement, i.e. when the arc plane is made to rotate about the second axis of rotation.
Another drawback of this arrangement, particularly for smaller systems without the benefit of motor-drive such as in the case of mobile surgical units, for instance, is that arc movements due to simple manual action by the operator can only be obtained by the rebalancing of the system, that is by placing counterweights outside the system rendering such systems particularly bulky. To underscore the extent of this problem, it will be noted that in some such small systems with the arc moved under manual action, the source of X-rays and the image chain receiver are each supported at the opposite end of the arc at positions well outside said arc i.e. such that the axis of the image chain is no longer on a diameter of the arc. This provides a solution to the problem of balancing but has the drawback of using a supplementary translation movement on each new angle of incidence obtained by the angle of the arc so that the axis of the image chain passes through the isocenter.
It will also be observed that another drawback of these isocentric stands is that it is necessary to add substantial and bulky resources to them, first to substitute the source and the X-ray receiver for one orientation of the image chain axis.